CUCHILLA INFERIOR REMALLADORA SINGER 842 COMPATIBLE CON BROTHER INDUSTRIAL COD. DE CUCHILLAS INFERIROR 112436001 SUPERIOR 144074001 Brother EF4-B511 EF4-B531 MA4-B551 Series ---------------------------------------------------------- Upper Knife & Lower Knife , Brother # 144074001 & 112436001 Brother Serger Models: B511, B531, B551, B631, B661, B957 SINGER 842U